4. Statistical Simulation of Plant Phenology Temporal Variation

To simulate temporal variation of plant phenology, daily mean air temperature-based temporal phenology models were constructed using Taraxacum mongolicum first leaf unfolding and common leaf coloration data at 52 stations within eastern China’s temperate zone from 1990 to 2009, and Ulmus pumila first leaf unfolding and leaf fall end data at 46 stations across China’s temperate zone from 1986 to 2005. Results show that the new model is more precise and rational in detecting responses of plant phenology to temperature than conventional monthly mean air temperature-based phenology models. Both T. mongolicum and U. pumila phenology shows a consistent response to temperatures at local and regional scales. Namely, first leaf unfolding date has a significantly negative response to spring temperature, while common leaf coloration and leaf fall end dates have a significantly positive response to autumn temperature. Moreover, a 1 ℃ increase in spring temperature may cause a larger advancement of first leaf unfolding date at warmer locations than at colder locations for both T. mongolicum and U. pumila, whereas a 1 ℃ increase in autumn temperature may induce a larger delay of leaf fall end date at warmer locations than at colder locations for U. pumila. Therefore, future regional climate warming may enhance sensitivity of plant phenological response to temperature, especially in the colder regions where the greatest climate warming is expected.